You will probably be fine with then Velleman unit, especially if your planning on keeping things simple.

VSA isn't one of mine, its Brookshire,s, the most significant product is DMXorcist, but if you wanted to go to a BoC servo drive then you will either have to use it at default settings or get an Enttec to reprogram it.

The problem with VSA is that you will only be able to play one routine to your DMX chain at a time, once you get into DMX that starts to become a major drawback.

DMXorcist was designed to fix that problem as it give you the opportunity to play up to 16 VSA routines at the same time over a single DMX chain, this means you could control an entire haunted house from a single computer over a single DMX chain, a couple of routines could be background loops for example, and you could have the rest tied to trigger switches or timers to play a routine on demand.

There is also plenty of free software that uses the Enttec, looking at the download page I count 20 free titles that work with Enttec (and Velleman), the software that comes with the Velleman is pretty limited, I recommend you take a look at freestyler, Im fairly sure its Velleman compatible.

I can understand why you thought the 3 pin connector was a saving, but as you get into DMX you will find that its a false economy, your going to need plenty of 5pin/3pin converters, 5 pin is the correct DMX standard, the problem with 3 pin is that its too easy to screw up your DMX network by using a mic cable instead of a DMX cable.

Watch out for cheapskate sellers on Ebay who sell you Mic cables instead of DMX and try and tell you Mic cables are fine, they are not.